ABSTRACT

Waves tides and currents exert continuous, and sometimes formidable, forces on the shoreline The response of the shoreline is a function of these forces together with the geological make-up of the seabed and the coast The nature of this response is a major factor in the process of determining the correct measures to defend the coast from erosion or from flooding This paper reviews the significance of these coastal forces and outlines some methods for determining them Three example cases are presented in the second part of the paper

INTRODUCTION

Severe storms during the winters of 1989/90 and 1991 caused extensive damage to the coasts of England and Wales The failure of the sea defences at Towyn in North Wales, and the flooding which resulted, probably received the most media coverage Damage to coastal defences was however widespread, at some locations, such as Eastbourne and Sidmouth, storms resulted in a significant loss of beach sediment This is a major concern as it lowers the beach and thus exposes the man-made defences behind to increased attack from the sea

These recent events have heightened public awareness to coastal and sea defence issues, an awareness made more acute by the topical debate over global warming and sea level base

It is the business of coastal engineers, both in the public and private sectors, to devise solutions to these problems Such solutions must recognise not only the need to carry out works to remedy immediate problems, but also to facilitate management of the coastline or more specifically the shoreline, over an economic scheme life In this context the scheme life is usually between 25 and 50 years

The appraisal and development of schemes entails consideration of several facets In broad terms these can be summarised by the following

  • Technical issues - the proposed scheme must

    • satisfy its primary functional requirements, eg avoidance of coast erosion and/or flooding

    • be sustainable for the targeted scheme life

    • not create problems elsewhere or for the future

  • Environmental Issues - The coast is both immensely valuable and extremely sensitive In environmental terms All major schemes require appraisal of the environmental Impacts of all relevant parameters which might include ecological, conservation, fishery, water quality, archaeological, visual and other human sensory Impacts This requires as a prerequisite a sound environmental database Extensive consultation is Invaluable

  • Economics - Engineering works for coast erosion and flooding are granted by MAFF In England, the Secretary of State for Wales or the Scottish Development Department To qualify for grant ad, the scheme must be demonstrated to be economically worthwhile Thiiss determined by accompanying the costs of a scheme with the benefits afforded by it The benefits are determined by assessing the value of damages avoided by the scheme The analysis must also take into account the reduced losses which may continue to occur after the scheme is in place, as it is not usually practical and not necessarily economic to eliminate all possibilities of damage

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